1. Field of the Invention (Technical Field)
The present invention relates to a rotary-driven recycling apparatus that reduces the article input size of tire chip and various other materials to a desired article output size.
2. Background Art
Today many materials such as worn rubber tires are recycled for resale on the market. Interest in tire recycling is relatively new. Serious attempts to recycle tires beyond using them for planters, door mats, and loading dock bumpers progressed very slowly until the mid-1980's. Even today tire-recycling processes are in the early stages of development, with the most dramatic progress taking place in the period since 1994. The first step in tire recycling is to take a whole scrap tire, and shred it into smaller chunks of material with fiber and steel interstitial to the rubber. In many cases, the shredded tire material, or "chip", is monofilled into landfills, stockpiled again, burned as tire derived fuel, or used as a feed stock in further processing. Further processing is often referred to as crumbing, wherein either whole scrap tires or tire chip is fed into a processing unit, and is reduced to a variety of mesh sizes for use in various products. Typical industry standard crumbing equipment requires a 1/2" to 3/4" tire chip input size in order to protect the crumbing equipment from excessive wear from the steel and fabric components in used tires.
Rubber crumb is a valuable source of raw material for new tires for automobiles, pavement for roads, playground surfaces, landscape materials, construction materials, shoes, etc. as well as for the extraction, petrochemical and petroleum-refining industries. Various sizes of rubber crumb can be sold on the market. As interest in recycling continues to grow, other materials--both heterogeneous and homogeneous--will be reduced to be used as raw material in the production of a multitude of goods.
The following is a discussion of present crumbing technologies and their limitations:
Cracker Mill Crumbing
Cracker mills reduce 1/2" to 3/4" inch rubber input size into a finer rubber output size by compressing the rubber to its shattering point. In most crumbing operations there are several cracker mills in succession to achieve a 10-mesh output size. Although the cost per unit is moderate, the need for several units becomes cost intensive. Several problems exist with this technology. These mills often operate at very high temperatures--as high as 400.degree. C. At around 250.degree. C., the chemical and structural integrity of rubber begins to diminish, and vulcanization and ash and carbon black contamination occurs. The heat generated by this process also creates a fire hazard. Furthermore, companies that produce crumb rubber in this manner cannot easily interrupt their system of mills to screen off different output sizes. Internal parts are often welded together and difficult to access locking them into a limited product line because just one size of output material is produced. Furthermore, mills of this type simply cut the article and do not separate the different materials, which make up the article, for example, the steel or cord, rubber, and fibrous matter which make up rubber tires.
Cryogenic Crumbing Technology
In cryogenic crumbing technology, scrap tires are frozen by introducing liquid nitrogen or other cryogenic fluid to them in a hermetically sealed canister causing the rubber to become brittle. The frozen rubber is then reduced by standard equipment to cause the separation of three components, rubber, steel, and fiber. In order for this system to produce large quantities of crumb rubber, the tires have to be shredded prior to freezing, and the crumbing throughput is directly related to the size of the tire chip coming out of the shredder. Cryogenic freezing is used to obtain a finer output size with less wear on standard equipment. However, this process adds an additional and costly energy-intensive step to standard systems. Furthermore, the effect of the cryogenic temperature on the thermophysical and chemical properties of the rubber makes it unsuitable for some applications.
Pyrolysis
Pyrolysis is an anaerobic process that can be used to convert scrap tires into their underlying constituent products, which include a mixture of carbon blacks and byproducts including ash, zinc oxides, carbonates, and silicates (collectively referred to as char and comprising approximately 37% by weight), pyrolytic oil (comparable to Number Six fuel oil), gas, and steel. Much of the gas is commonly used as an energy source to drive the chemical reaction, which takes place in a refinery-like apparatus. Pyrolysis typically requires a multi-million dollar capital investment, and the economic viability of products based on this technology has not yet been demonstrated in the marketplace.
Buffing
When a waste tire is taken to a recapping shop to have a replacement tread installed, the old tread is buffed off from the casing. The buffings produced in this manner are generally considered to be of high quality and small mesh size. However, these buffings tend to be geometrically elongated in one direction making them unappealing for some applications.
Machines performing the various crumbing processes are typically quite large, have high electrical power consumption, high incidence of replacement parts, low efficiency, high maintenance costs, high running temperatures, overheating or cryogenic embrittlement of the rubber, and poor operating convenience. Rotors are often jammed when the chunk load rate is increased to a point exceeding the maximum torque capability of the drive system causing an immediate increase in the electric current driving the machine and a potential for drive system failure. Furthermore, rubber, which has lost its chemical structural integrity due to high operating temperatures, must be treated with chemical additives resulting in tremendous expense. And, in order to obtain the desired rubber output size, several passes through the machine are necessary.
Patents disclosing shredders, grinders, and mills quite different from the present invention include: U.S. Pat. No. 4,151,794 to Burkett, entitled "Apparatus for Treating Organic Materials"; U.S. Pat. No. 3,987,970 to Burkett, entitled "Centrifugal Mill"; U.S. Pat. No. 4,637,561 to Edberg, entitled "Beater Mill Having at Least One Vertically or Obliquely Extending Cylindrical Milling Chamber"; U.S. Pat. No. 4,469,284 to Brubaker et al., entitled "Comminuting Apparatus With Improved Rotor and Stator Recess Construction"; U.S. Pat. No. 4,614,310 to Tloczynski et al., entitled "Comminuting Apparatus with Fluid Cylinder Rotor and Stator Biasing"; U.S. Pat. No. 2,359,911 to Grindle, entitled "Pulverizer"; U.S. Pat. No. 1,758,010 to Pettinos, entitled "Grinding Mill"; U.S. Pat. No. 5,577,675 to Ishikawa, entitled "Agitating Pulverizer"; U.S. Pat. No. 5,522,559 to Bredbeck, entitled "Rubber Crumbing Apparatus"; U.S. Pat. No. 4,747,550 to Jackering, entitled "Grinding Mill with Multiple Milling Sections"; U.S. Pat. No. 3,851,829 to Dopper et al., entitled "Device for Crushing Solid Materials"; U.S. Pat. No. 1,636,033 to Agnew, entitled "Centrifugal Impact Pulverizer"; U.S. Pat. No. 4,133,487 to Lanier, entitled "Method and Apparatus for Comminuting Solid Article in a Fluid Stream"; U.S. Pat. No. 5,373,996 to Hamada, entitled "Granular Material Processing Apparatus"; U.S. Pat. No. 5,257,742 to Yashima et al., entitled "Ultrafine Grinding Mill of Which Fed Material Flows Down Through an Agitated Bed Composed of Small Grinding Medium"; U.S. Pat. No. 4,919,347 to Kamiwano et al., entitled "Dispersing and Grinding Apparatus"; U.S. Pat. No. 4,383,650 to Contal et al., entitled "Method and Apparatus for Grinding Rubber"; U.S. Pat. No. 2,211,518 to Scherbaum, entitled "Grinding Mill"; U.S. Pat. No. 3,448,932 to Prohl, entitled "Waste Disposal Devices"; U.S. Pat. No. 3,260,468 to Beard, entitled "Grinding Mill and Blower Combination"; U.S. Pat. No. 2,609,995 to Klagsbrunn, entitled "Centrifugal Mill"; U.S. Pat. No. 1,798,465 to Grindle, entitled "Coal Mill"; U.S. Pat. No. 1,669,239 to Grindle, entitled "Pulverizer"; U.S. Pat. No. 4,757,949 to Horton, entitled "Apparatus for Shredding Rubber Tires"; U.S. Pat. No. 4,029,263 to Wilkinson et al., entitled "Ballistic Pulveriser Separator"; and U.S. Pat. No. 1,653,472 to Scherbaum, entitled "Pulverizing or Grinding Mill." None of these patents disclose removably attachable and interchangeable interior configurations, the ability to produce variable output sizes, unique air flow systems, feedback control systems, or unique size-reduction techniques which impact the article to be reduced and utilize the heterogeneity of the article to further aid in size-reduction.